As solid-state disk (SSD) technology closes in on hard disk drive (HDD) capacity and price, experts say it may not be long before spinning disks are a thing of the past and a computer's storage resides in flash memory on the motherboard.

By making the drive part of a system's core architecture -- instead of a peripheral device -- data I/O performance could initially double, quadruple or more, according to Jim McGregor, chief technology strategist at market research firm In-Stat.

"Instead of using a SATA interface, let's break that and instead of making it look like a disk drive, let's make it look like part of the memory hierarchy," McGregor said. "Obviously, if you break down that interface, you get more performance."

A 1.8-in solid state drive

Currently, Serial Advanced Technology Attachment (SATA) is the bus used to transfer data between a computer and storage devices, be it HDDs or SSDs in a 1.8-in., 2.5-in. or 3.5-in. disk drive form factor. SSD manufacturers have been fitting SSDs into a hard disk drive case to fit it into existing computer architectures.

Within three years, McGregor said SSDs with 256GB capacity -- already on the market -- will be close to the same price as hard drives. (A 256GB SSD for the new 17-in. MacBook Pro from Apple is a $900 build-to-order option, for instance. A 250GB HDD goes for about a tenth that price.) That will signal to manufacturers that it's time to consider an interface change. And, while SSDs will be lagging behind the 500GB to 1TB capacities of hard disk drives for some time to come, McGregor argues that users don't need that much storage anyway.

"We've already seen this trend in the netbook space, and we will see it more in the notebook platform. Storage will begin to look more like a memory module than a hard drive," said Dean Klein, vice president of Micron Corp.'s SSD group. "There's a move afoot to make it more like a card-edge connector, so the SSD would not have the cost of a mechanical connector. It would just have gold-plated fingers on the edge: No enclosure, just the circuit board."

Disk drive vendors are doubling the capacity of drives every 12 to 18 months, but In-Stat's data indicates that the average storage requirements of users increase in a more linear way. And, while HD video can drive a huge swing in storage requirements, the advent of online libraries and storage services tend to even out the trends, McGregor said.

According to In-Stat, SSD prices have been dropping 60% year over year. Currently, the price of consumer-grade SSD costs from $2 to $3.45 per gigabyte, with hard drives going for about 38 cents per gigabyte, according to Gartner Inc. and iSuppli Corp.

"Two years ago, SSDs cost $17.50 per gigabyte, so it's obvious that consumer NAND flash memory will soon be a true contender to hard disk drives -- it's just not there yet," Gartner analyst Joseph Unsworth said. "I think you need to get to 128GB for around $200, and that's going to happen around 2010. Also, the industry needs to effectively communicate why consumers or enterprise users should pay more for less storage."

Klein argued that using an SSD in its native state, as NAND chips on a board without an enclosure, will reduce cost, weight, power use and space.

In January last year, Lenovo launched the Lenovo ThinkPad X300, the industry's first mainstream notebook designed not to take a hard drive, but a 64GB SSD. Dell followed IBM with its all-SSD Latitude D420 ultra-mobile and D620 ATG semi-rugged notebooks.

"Moving forward people will design the entire notebook around SSD. You could spread SSD out over the mother board. So moving forward there will be a lot of custom notebooks with custom SSDs," said Brian Beard, marketing manager for Samsung's flash memory group.

Samsung, which sells laptops, not only manufactures and sells HDDs, but it's own line of SSD as well as selling flash memory to other vendors to resell.

Beard expects SSD penetration in the laptop market will only reach 30% by 2012, but he also believes around the same time HDD and SDD will reach price parity.

Within the next year, Micron expects to bring to market a high-end SSD that could achieve 1GB/sec. throughput by using a PCIe interface rather than traditional SATA or SAS. The transfer speed is four times that offered by Intel's newest, enterprise-class SSD, the X25-E.

In a video on Micron's blog site, Joe Jeddeloh, director of the vendor's Advanced Storage Technology Center, demonstrated the technology using a two-processor, eight-core Intel Xeon PC and a card with two SSDs and 16 flash channels. A blurry readout showed the SSD reaching 800MB/sec. throughput, with Jeddeloh claiming that it "will be hitting a bandwidth of 1GB/sec. and at least 200,000 IOPS," or I/O operations per second.

The card was directly connected to a PCI Express (PCIe) slot, bypassing SATA or Serial Attached SCSI interfaces. While PCIe has the same throughput as SATA II -- 3Gbit/sec. -- PCIe offers more channels.

Using file transfers ranging from 2KB to 2MB, Jeddeloh demonstrated 150,000 to 160,000 random reads per second in the video. "That's what flash can do when it's managed correctly," he said.

NAND flash boards

While Micron's SSD technology is aimed at high-end applications that would run on Fibre Channel SANs, such as transactional databases or streaming video, Klein said consumer-grade computers using SSDs directly connected to a PCIe bus with four lanes (x4 slots) could soon achieve similar results.

Physical PCIe slots may contain from one to 32 lanes of data. Currently, PCIe Generation 1 offers 250MB/sec. throughput per lane. The second generation of PCIe is expected out next year and will offer twice the throughput, or 500MB/sec. per lane. While SATA 3.0, expected out this year, also doubles throughput, it only offers one lane.

"Each lane of that x4 PCIe is as fast as a SATA 3.0's 6Gbit/sec. bus," Klein said. "So I can be four times as fast on that one slot as an SSD could be on a SATA 3.0 connection. That's really the direction things are going."